Tucson Electric Power Co. asked the agency, which sets utility rates, to let it double its basic monthly service charge for residential customers, from $10 to $20 per month, as well as assess new fees, penalties, and charges on rooftop solar customers. A study done by the utility says that customers with solar panels, on average, shift $67 a month in costs to non-solar customers because they pay less for grid upkeep.

The fight has the potential to go to the courts and set standards nationwide,